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Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Saturday - February 09, 2008

From: Portland, OR
Region: Northwest
Topic: Herbs/Forbs
Title: Rubber (latex) in Balloon plant (Asclepias physocarpa)
Answered by: Nan Hampton

QUESTION:

I need milkweed leaves that contain rubber. The common milkweed species Asclepias syriaca has rubber in it. Do the milkweed of Balloon plant milkweed (Asclepias physocarpa) contain rubber?

ANSWER:

Asclepias physocarpa is a native of southeast Africa and our focus and expertise is on natives of North America so this plant is not really in our purview. However, we can answer your question. The majority, if not all, of the milkweeds—in particular, the members of the Genus Asclepias, including A. physocarpa—contain the sticky white latex sap that you see when you cut or break the leaves or stems. The latex, plus other chemical components such as cardenolides, are the plants defense against herbivores. There are insects that do thrive on the milkweeds (e.g, the monarch butterfly, Danaus plexippus) and have devised strategies to subvert the plants's defenses. You can read more about the plants defense strategies in: Angrawal, A. and M. Fishbein. 2006. Plant Defense Syndromes. Ecology 87(7) Supplement. S132-S149.

 

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